Bearing manufacture



Oct. 31, 1939. .1 wfs. c LKINs ET AL 3.5 9

' x BEARING MANUFTACTURE Original Filed May 1, 1936 2 Sheets-Sheet 1 IVNVENYTOR WILLIAM A GAL/0N6 4N0 ANTHO YcI. L/VNGH/IMMER.

a miu. i411 -wm. Afro RNEY Oct. 1939. w. G. cAL ms ET AL 1 BEARING MANUFACTURE Original Filed May'l, 1956 2 Sheets-Sheet 2' -----c------r--------:--:::2111:112:2:111?212.2122 r l INVENTOR W/LL/AM G. CALK/Ncs III/D ANTHOIg/XX J. LANGHAMMER.

ORNEY i iurtherobject ofthe invention is to provide an improved jporous metalbearing material which will bond directlytoreinfo'rcing backings Patented Oct. 31,1939

2,178,529 BEARINGI MANUFACTURE William G. Calkins and Anthony J. Lang-hammer,

Detroit, Mich., assignors to Chrysler Corpora ftion, Highland Park, Mich a corporation of UNiTED STATES,

Delaware .PATENTI oFFicE Application ay 1, 1936, Serial No. 71,324 I Renewed'May 1'7, 1939 I 14 'Claims. (Cl. 29-4495) This invention relates to improved bearing materials and to an improved method for making the same and for making bearing material- I including articles.

' "More particularly the invention pertains to.

improvements inbearings having'porous ,n 'etal bearing surfacesof the character which have a substantial lubricant absorbing capacity. 1

One of the main objects. of the invention is l0 to provide porous metal'bearing material in the ."form ofsheet-stock which maybe employed'in I itsfiat'shape or readily formed to a desired" contour.

II :Another object o f'the invention is to provide it sintered porous' inetal bearingmaterial of sheetflike form having mixed particles of different powdered metals substantially integrally bonded together and which also includessolid lubricating material;

I A further object of the invention is to provide an improved mixture of finely divided constituents'of porous metal of this character that'is v particularly adapted for theformation of sheet:

1 like briquettes which in {their compressed, but

j unsintered state, aresufficiently fiexible to ac- I commodate substantial fi'exure duringtproduction and subsequent handlingjwithout fracture.

Another object of the invention is .tofprovidef I i an improved solid lubricating agent in porous] no'metal forming powdered mixtures of this kind which enables sheet-like briquettes formed therefromto bebent a substantial amount during'han'dli'ng without breaking thecontinuity of I the briquette structure.

A still further objectfofi the inventionilis to provide an improved finished and sintered shcetlike bearing'material of this kind which'may: be

deformed to a comparatively "large variety of shapes and whichissufliciently flexible to with- 40 stand repeated fiexure without failure.

:Another object of the invention 1 to provide a an improved composite bearing member which has porous metal surface providing elements and 5 a reinforcing backing rigidlysecured theretopor which may be'bonded thereto by soldering or brazing. v

i011 Still further objects of the invention are to provide improved methods for manufacturing sheet-like porous metal bearing material and to provide a continuous process of this character by which comparativelylong strips, of such mal'.'sf terialv can bemade in a continuous manner.

1 9 is a longitudinal I naoe showing apparatus thereinembodying a modif ed-form of theginventionFfor "efiectirig a a continuous bondingito'gether'of elongated ribs bons of porous metal bearing material and sheet A still further object of the invention is to provide an improved method for continuously applying elongated: strips of sheet-like porous metal bearing material; to correspondingly elon gated stripsgof reinforcing backing I ne taL: .5 I

An illustrative embodiment of the invention is shown in the accompanying drawings, in

our improved porous metalvbearing material in" superimposed relation'on a reinforcing backing I and havinga layer'of bonding alloythcrebetween.

[Fig 4 is an illustrational side elevationalview go showing the superimposed backing and bearing .material layers of Fig. 3 in 'a jclamped relation suitable for the application of heat to effect a bond between the layers.

Fig. 51s a diagrammaticlongitudinal sectional view of a furnace iorheating thef'backing and bearing material illustrated'jin Figfd to effect a I i bondtherebetween.

Fig.6 isa fragmentary, vertical; sectional view I I of I die/forming apparatus by which a finished ao j blank comprising a backing and a layerof porous metal bearing material may be broughtto semi-cylindrical shape; I I I I Fig. 7 isa fragmentary, sectional view of die.

' forming apparatus for performing thefinitial forming operation-upon a] bearing. blank pre- II paratory tobringingit to'fii'ial cylindrical shape.

Fig.8 is a fragmentary sectional view of die forming apparatus for completing the cylindrical; II I I formation which the apparatus shownin'Fi'g; 7 40 Y is'adapted to commence. I

bac'ing materialq I 1 'lng't'ne 'form' of the-invention illustrated in the drawings," our improved porous metal forming 0 methodmay be performed with'apparatus whiclrr includes asupportllii on which ismounted ag I fiamefstructure comprising spaced side members ll aIfdf lZ which are secured together and heldin fixed spaced relation .by 'transversez bars Iii- I 5 5 sectional view of a' fur? Each side member H and I2 is provided with a slot. I4 extending inwardly from its right vertical edge. as viewed in Fig. 1, in which is slidably mounted a block having a bore l6 formed in its inner end. Each block I5 has outwardly extending flanges l! on its external end provided with apertures through which threaded studs l8, rigid- 1y mounted in the frame side members H and I2, respectively, extend. Threaded on each stem I8 is a pair of nuts l9 between which the flanges IT'of the block l5 are disposed. The nuts is may be adjusted to selectively position the blocks l5 in their respective slots 14 and to maintain the blocks against unintended movement.

Journalled in the bores l6 of the slidable bloc i5 is a shaft which extends transversely of the frame structure and on the intermediate portion of which is rigidly mounted a roller 2| having spaced grooves 22 formed in its periphery. A gear 23 is also non-rotatably fixed to the shaft ill and disposed adjacent the side member |2 of the frame structure. The shaft 28 is held against axial movement relative to the slide blocks l5 by collars 2t and which are fixed on its respectively opposite ends and disposed externally -01 the frame structure, the collar 24 being located adjacent the slide block l5 of one side frame inember and the collar 25 being disposed adjacent the gear 23.

The side members H and I2-of the frame member are provided with registering bores 26 in which are journalled a transversely extending shaft 21 having a roller 28 non-rotatably mounted on its intermediate portion and disposed between the sides l! and i2 of the frame. The roller 28 has external ribs 29 on its periphery which fit into the'grooves 22 of the roller 2i in order to provide a passage between the peripheries of the rollers 2| and 23 having sharply defined edge extremities. Non-rotatably mounted on. the shaft 21 is a gear 30 having teeth thereon meshed with the teeth of the gear 23. One end of the shaft 21 is provided with a driving member, diagrammatically illustrated at 3|, which may comprise a gear, pulley or other suitable means by which the shaft 2'! and roller 28 thereon may be rotated by a suitable motor or other prime mover. The peripheries of the rollers 2| and 28 may be adjustably positioned with respect to each other by manipulation of the nuts H! on the threaded stems 18 which are adapted to shift the slidable blocks l5 inwardly and outwardly with respect to the slots of the side members H and I2 of the frame in order to bring the peripheries of the rollers 2| and 2B closer together or further apart as desired. In this manner. the thickness of the article compressed between the rollers may be conveniently predetermined. The diameters of the rolls 2| and 28, as well as their spaced relationship, are preferably predetermined to facilitate the formation of briquettes of different thicknesses. It is found that more satisfactory results are obtained by reducing the diameters of the rolls as the thickness of the strip formed therebetween is decreased, and increasing the diam- 'eters of the rolls as the thickness of such strip is increased.

Mounted on the frame structure of the porous metal forming apparatus shown in Fig. 1 is a hopper 32 having an intermediate portion 33 of somewhat cylindrical cross-section in which is mounted a dispensing device 34 having radially ex-- tending vanes 85. The dispensing device 34 is non-rotatably mounted on a shaft 36 journalled in the side walls of the intermediate portion 38 of the hopper and this shaft is drivingly connected by gears 3'! and 38 with the gear 23 by which the roller 2| is driven in timed relation with respect to the roller 28 and gear 30. During operation of the rollers the dispensing device 34 is rotated in timed relationship therewith so as to discharge measured quantities of the contents of the hopper from .the latter at a rate propor tional to the speed of operation of the rollers. The hopper 32 has a downwardly extending tapered discharge spout 38 which is adapted to direct the material discharged from the hopper into the space between the rollers 2| and 28 and between the ribs 28 of the roller 28. Mounted on the frame structure of the forming apparatus is a vibrator, generally designated by the numeral Hill in Fig. 1, by which the discharge spout J8 and walls of the hopper 32 can be vibrated to feed powdered material to the rolls. This vibrator includes an air cylinder |0|, piston I02, and

piston rod I03 engaging the discharge spout 38 and suitable valve mechanism (not shown) by which vibratory movement of the piston is controlled. A scraper 39 is pivotally mounted at 40 on the side member l2 of the frame structure and is provided at its upper end with a knife edge which is yieldably held in contact with the periphery of the roller 28 by a coil spring H. as illustrated in Fig. 1.

A similar scraper 42 is pivotally mounted at 43 on the side member i2 of the frame structure and yieldabiy held in contact with the periphery of the roller 2|, and particularly the portion thereof between the groove 22 of the roller 2| by a counterw ight 44 which normally tends to rotate the scraper 42 in a clockwise direction as viewed in Fig. 1.

Disposed between the scrapers 39 and 42 is a. support 45 having an arcuately curved end portion projecting to within close proximity of the peripheries of the rollers 2i and 28 which is adapted to receive the ribbon of sheet-like porous bearing material compresed between the rollers 2| and 28 and to guide the movement thereof in a curvilinear course of relatively large curvature as the compressed ribbon is discharged from the pressure'applying apparatus. The opposite end portion of the support 45 is substantially horizontal and it is constructed and arranged to direct the ribbon of compressed constituents of the porous metal toward the inlet end of a furnace i6, hereinafter more specifically described. Any desired combination of constituents of porous metals may be placed in the hopper 32 and fed therefrom by the dispensing apparatus 34 to the rollers 2| and 28 by which the material, which is usually in a very finely divided state, is compressed to the form of a sheet-like briquette of any desired thickness, the length of the briquette being determined by the amount of the powdered mixture supplied to the hopper 32 and the thickness thereof being predetermined by the size and adjustment of the rollers 2| and 28 in the foregoing manner.

While a large variety of mixtures of powdered metals and other ingredients may be used, it has been found that the following compositions produce briquettes which, in their unsintered state, will accommodate considerable deflection in order to facilitate continuous removal of the ribbon of compressed powdered materials from the rollers to the furnace in which it is later sintered.

. Powdered'boric acid Powdered copper 77 ,.No.1 I Percentby pweight No.2 I

Percent by weight j Powdered 'boric acid Exfoliat'e'd mica 1 Powdered copper 88 weight Powdered 'copper .t. 20 Powdered graphite 15/ Powdered iron j 77.5

The percentages of the materials used in. the foregoing compositions may be varied'within substantially wide limits, the particular proportions recited being givenmerely as examples of compositions which, it has been found, may be readily compressed into sheet-like briquettes in a con tinuous'briq'uetting process of the foregoingtype. The graphite incompositions Nos. 1 an'd 3 and the'mica in composition No. 2 serve as alubricant during the compression operation and also remain in the finished producttoenhanc'e the lubricating properties thereof. Any suitable. solid lubricating material may be used in place of mica and graphite and in some mixtures liquid lubricant such as fordinarylubricating oil may 'beemployed. Mica and graphite have, however been found to impart a desirable high degree of flexibility to the compressed briquette, which serves prior to sintering to guard against fracture of the ribbon-like'briquette discharged fromthe rollers duringhandling thereof.

The boric acid also serves as a lubricant during the compressing operation and it has a further purpose the fiuxing of the compositionduring the sintering operation. Other combined fluxing and lubricating agents, such as stearic acid, p01 mitic acid and salicylic acid, may be used for this purpose.

The terminology bearing material and fpor ous bearing metal appearing in the specification and'claims is used in its broad sense andshould beco'nstrued to lncludefrictional, such as that employed in lining brakes and clutches, as well as anti frictional materials. In many frictional applications, porous metal formed from powdered mixturesof the foregoing compositions are satisfactory, particularly when the lubricant impregnating operation is omitted."

Sheet-like porous" metal, particularly adapted 1 j for applications where a relativelyflhigh, coefli Lea cient of friction is desired, such as in clutch and brake linings,-cla;nbe formed in the foregoing manner from a mixture of powdered'constituents having the followingcomposition:

Graphite Asbestos HOIHUIQ i 2,178,529 I g,

l 'I'he' asbestos of the above composition which 7 Percent by Y 1 thickness are not permissible.

or cut into desired lengths for future use.

sheet-like porous metal may be used, in some apemployed for bearing surface purposes.

serves towincrease the coefllcientof friction of aluminum oxide, magnesium oxide, silica or talc in substantially the same proportion.

The furnace 45 is disposed adjacentthe discharge end ofthe support 45 and it has an inlet opening .41 whichregisters with. the latter. Disthe resulting product can. be substitute'd forfby posed in substantial alignment with the upper surface of the support 46 isa conveyor belt 48 which is movablysupported onspaced rollers 49' mounted-on the opposite ends of the, furnace 46. g

The upperside of the conveyor 48 extends through the interior!!! of the furnace and, through an outlet opening i which registers with the inlet opening 41. As the continuous sheet-like briquette leaves the discharge end of th support 45, it isdeposited upon the belt 48 of the conveyor by which it is-gradually drawn through the interior of the furnace 46 which preferablyhas a non-oxidizing or reducing atmosphere. A suitable atmosphere may be. provided by supplying either hydrogen or illuminating gas of a reducing" character to the interior of the furnace. 1 The" furnace'is preferably maintained at a tempera- "ture slightly above the melting point of one of thepowdered'metal constituentsof the mixture of which the briquette is formedand below the melting point ofthe other metal.

If morethan two metals are employed in the mixture then the sintering temperature may be above thi melting point of two of the metal constituents thereof but below the melting point of the other. The par-:11-

ticular temperature is', of course predeterminedg bythe. character of the constituent of thepowder ed mixture of which the briquette is formed. The conveyor belt 48 is preferably driven by driving mechanism (not shown) which may be ODQI'a tively connected with one of the pulleys 49; 1 V After the ribbong-like 'briquette has been ;sin-

tered, it may be deflected while unsupported, as 1 illustrated in the lower portioniof Fig. 1 inorder" to submerge itin an oil bath 54 so asto impreg-f hate the porous metal structure"with a suitable lubricant. This lubricant impregnating step may,'if desired, be omitted completely or delayed -until after the bearing material has been made up into final form.

After the lubricant impregnating operation or, in the event this step is not employed, after the sintering operating, the ribbon-like strip is passed continuously through a pair of sizing rolls 53' by which it may be brought'to a desired thickness] for use inapplicationsvvhere slight variations in then The sintered ribbon of porous metal may be wound into aroll upon a reel, (not shown).

plications, in its relatively flat state or itma'y be The In-Figs. 3 1509, inclusive, is illustrated one application of our improved porous'metal sheeting which comprises the formation of reinforced stances it is desirable to solder or braze the porous metal layer to the reinforcing backing. This may formed to any desired curvilinear contour and be conveniently accomplished by placing between.

the two layers an intermediate film SI of powdered solder or brazing compound or sheet foil 6i comprising such compounds and a suitable flux. The bonding metal may also be deposited on the sheet metal or porous metal by electrical plating or deposition. The superimposed layers of reinforcing backing material and porous metal either with or without an intermediate film of soldering or brazing alloy may then be placed under compression in a clamping device generally designated by the numeral 62 and shown in Fig. 4. The

clamping device 62 includes a base plate 53 and a spaced bail-like structure 54 having a threaded opening 65 in its central portion in which a set screw 66 is threaded.

Disposed between the lower end of the set screw 55 and the upper layer of the structure being clamped is ablock 5! which is firmly held by the screw 66 and clamped in clamping engagement upon the superimposed layers of reinforcing and porous metal. Thesuperimpoced layers 59 and Gil are then firmly bonded together by the application of heat thereto while they are so held under compression. This may be conveniently accomplished by passing them, while held in their clamps, through a furnace 68 which preferably had a reducing or nonoxidizing atmosphere. A plurality of clamps containing layers of rcinforcing material and porous metals may be successively passed through the furnace 68 by supporting the clamps in which they are disposed through the furnace on an endless conveyor 69, in the manner illustrated in Fig. 5.

successively adjacent portions of elongated ribbons of porous metal may be continuously bonded to corespondingly elongated ribbons of sheet metal backing material by the apparatus illustrated in Fig. 9. This aparatus includes a rack. diagrammatically illustrated in Fig. 9. which comprises a pair of spaced side members 10, only one of which is shown. The side members 10 are provided with registering notches H for rotatably supporting reels [2, l3 and '74 comprising ribbons of porous metal, brazing or soldering foil and reinforcing sheet metal respectively. The ribbons from the reels 12,.13 and M are fed in superimposed relation by a pair of mechanically driven rolls 15 through a furnace 16 which is heated to a temperature sufficiently high to effect a bond between the reinforcing backing material and the porous metal. The latter layers of ribboo-like material are compressed together between pressure rolls 11 which are located within the furnace l6 and preferably far enough from the inlet end thereof to allow the material to be heated before pressure is applied. There may be may be omitted. In this case it may be foundto be necessary to raise the temperature in the furnace Hi substantially above the temperaturere quired for a brazing or soldering operation.

The composite stripof reinforcing and porous metal may be then rewound on a reel and stored for later use. It may be conveniently cut into lengths of desired dimensions and employed in a fiat state or in any desired curvilinear contour.

In Fig. 6 is diagrammatically illustrated die forming apparatus by which a composite piece of reinforcing sheet metal and sheet porous metal may be conveniently brought to semi-cylindrical shape. This apparatus includes a die part 18 having a cavity 19 therein to which a bearing member blank formed in accordance with the foregoing method may be pressed to semi-cylindrical shape by a ram or die 80. i

In Figs: 7 and 8 is illustrated the formation pf a cylindrical bearing member from a. piece of composite stock produced in accordance with the foregoing method. Initial operation may be conducted in a die part 8| having a cavity 82 therein. of U-shaped cross-section into which the bearing member blank may be forced by a. die part 83, as illustrated in Fig. 7. The preformed blank may then be transferred to a die, of the character illustrated at 84 in Fig. 8 wherein the parallel side portions of the preformed blank may be conveniently wrapped around the mandrel 85 by a plunger or die part 86 having a substantially semi-cylindrical cavity 81 in its end portion.

In the formation of bearing members of this character, the porous metal layer is preferably disposed internally, but if desired, this condition may be reversed to bring the porous metal layer to the exterior of either a cylindrical or semicylindrical bearing member.

Bearings made in accordance with our invention have a comparatively large lubricant absorbing capacity and in many installations may at their place of manufacture be provided with sufli cient lubricant to last throughout their normal life. When reinforcing backings are employed. the resulting bearing member is materially strengthened and the porous metal layer thereof is protected from breakage both in service and in shipment. If desired, the seams of the cylindrical bearing shown in Fig. 8 may be welded or otherwise fixed together. Both cylindrical and semi-cylindrical bearings of the above types can be accurately brought to a desired internal diameter by a breaching operation in the same manner as conventional cast bearings are finished.

The foregoing processes for the manufacture of porous metal bearing material and for the manufacture of reinforced porous metal bearings are well suited for high production requirement and the porous bearing metal may be manufactured and conveniently shipped to substantially any distant point for later fabrication into bearing members.

Although but several specific embodiments of the invention are herein set forth, it is recognized that various changes of the materials used and operations involved may be made without departing from the spirit and scope of the invention.

We claim:

1. The method of manufacturing sheet porous metal which comprises continuously feeding a charge of a mixture including powdered metals having different melting points directly between opposed arcuate surfaces of a. pair of pressure rolls to compress said charge uniformly from re- -spectively oppositesides into sheet-like briquette form, and then heating the latter to a sintcring temperature in a furnace having a non-oxidizing atmosphere.

dered: metalsjhaving diiferent melting points di rectly between Opposed arcuate surfaces of a pair of pressure rolls during rotation of the latter and at a rate proportionate tothe speedofoperation of said rolls so as to compress saidcharge substantially identically from respectively oppo- I site sides thereofinto sheet-like briquette form,

and then heating the latter to a sintering temperr metal which comprises continuously feeding a Y charge of a mixture including powdered lead, tin,

'ature in a furnace having a non-oxidizing atmos phere. I

31Tbemethod'of manufacturing sheet porous metalvvhich comprises continuously feeding amixture comprising finely, divided particles of clifierentmetals directly between a pair of. driv-. ingly rotated pressure rolls, so as to compress j said mixture uniformly f 'r'omirespectively opposite sides into sheet-like briquette form, direct ing the latter "continuously asfit discharged 1 from said rolls toward the inlet end of a furnace,

moving said compressed sheet-like briquette continuously through said furnace while subjecting it tofla 'sintering temperature therein, and discharging the sintered product while heated into i "an oil bath to saturate the pores thereof with oil.

. dl The method of manufacturing sheetporous graphite and copper and a fluxing agent directly I through and between mutually drivingly rotated pressure rolls so as to compress saidcharge uniformly from respectively opposite directions into sheet like briquette form, and then heatingthe W latterto a sintering temperature in a reducing 1' atmosphere. V v I )5. The method of manufacturing sheet porous mixture including powdered tin and copper and metal which comprises feeding a charge of a exfoliated mica and a fiuxing agent having lubrieating properties directly through and between mutually drivinglyrotated pressure rolls so as to subject said charge to substantially the same .unit

pressure from respectively opposite sides and to 1 'oompressthe same to sheet-like hriciuette form, and then heating the latter to a sintering temperature in a reducing atmosphere. 1

6. The methodoi making a bearing membe which comprises rigidly bonding a substantially fiat sheet-like piece of compressed and sintered porous metal of relatively small thickness to a sheet metal backing of substantially fiat contour, and then deforming the resulting composite structure to'a desired shape. H

7. The method of making a bearing member *whichcomprises rigidly bonding a substantially flat sheet-like piece of compressed and sintered porousmetal ofjrelatively small thickness to a sheet metal backing of substantially flat contour, and then bringinggthe resulting structure to tubular shape with said internally. 1 e e ii. The method of making a bearingmember porous metal disposed which comprises rigidly bonding a substantially 'iiatsheet-like piece of compressed and sintered porous metal of relatively small thickness to a "sheet metal backing oi substantially flat contour,

andthen formingthe resulting structure to substantially semi-.cylindrical shape between dies with the porous metal arranged internally of th resultingsemi-cylindricalstructure.

9. The method of making bearing members whichcomprises forming an elongated sheet of porous metal, disposing said sheet of porous sides with substantially equal unit pressure by passing thesame directly between pressure rolls 3 with said porous metal strip disposed internally.

said out portions of said composite assemblyto a desired contour.

ingly elongated strip of, reinforcing backing metal, subjecting said strips to heat and pressure to bond the same together, cutting'the re-, sulting composite strips of porous and reinforc-' ing metals into blanks having 'a surface area and dimensions corresponding to the surface area and dimensions of adesired bearing mema her, and bringingsaidcomposite strip to a detiredcurvilinear shape. I

10. The method of making bearing members which comprises forming an elongated strip of sheet porous metal, forming a correspondingly eiongatedstrip of reinforcing sheet metal, disposing said strips in superimposed relation with a bonding alloy interposed therebetween, subjecting said strips toheat and pressure to bond the same together, cutting the resulting comwhich comprises compressing a mixture including different powdered metals and aflux having lubricating properties from respectively opposite to'form a porous sheet-like elongated briquette, sintering said briquette. in a non-oxidizing atmosphere, disposing the resulting sheet-like strip of porous metal on'an elongated reinforcing strip of sheet metal, bonding said strips together, cutting 3 the resulting composite strip into blanks having a substantially flat surface area and dimensions corresponding to the surface area and dimensions of a desired bearing member, and bringing said composite strip to a desired curvilinear shape 12. The method of making sheet-like porous metal articles which comprises mixing together powdered lead, powdered tin, exfoliated mica, a preponderance of powdered copper and a fiuxing agent having lubricating properties; compressing said mixture to a briquette of sheet-like contour, and sintering said briquettejin a non oxidizing atmosphere.

13. The method of makingan article having a surface comprising bearing material which in- V clu'des the steps of forming from powdered material an elongated ribbon of porous metal, disposing said ribbon of porous metal adjacent a surface of a correspondingly elongated strip of reinforcing backing metal, subjecting the resultmetal in superimposed relation on a corresponding assemblyto heat andpressure to bond said i ribbon and strip together, cutting the resulting composite assembly into blanks, and bringing 14. The method of manufacturing sheet porous metal which comprises feeding a charge includ ing powdered metal directly between a pair of drlvingly rotated pressure rolls, so as to compress said charge uniformly from respectively opposite sides into sheet-like briquette form;'and

then heating the latter to a sintering temperature in a furnace having a non-oxidizing atmosphere.

WILLIAM G. CALKINS. ANTHONY J. LANGHAMMER. 

